water heater replacement

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mbrooke said:
I politely challenge this. To my knowledge there is nothing in any standard that requires and external OCPD to protect internal appliance wiring.
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So UL listing for equipment does not allow the manufacturer to limit fault current during the testing with an external OCPD?
That does not seem right to me.
Remember the NEC requires the field electrician to follow listing instructions from the manufacturer!

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GoldDigger said:
So UL listing for equipment does not allow the manufacturer to limit fault current during the testing with an external OCPD?
That does not seem right to me.
Remember the NEC requires the field electrician to follow listing instructions from the manufacturer!

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Show me the requirement.


jumper said:
Please do the math and then use the NEC to look up what you would be do using standard resi methods.

4500W WH, NM wire.

Beyond the fact that instructions say anyways.
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240 volts= 30amps breaker #10

208= 25 amp breaker #10


Installing a water heater is one thing, whether the OCPD is intended to protect the wiring in the heater is another.
 
mbrooke said:
Show me the requirement.




240 volts= 30amps breaker #10

208= 25 amp breaker #10


Installing a water heater is one thing, whether the OCPD is intended to protect the wiring in the heater is another.
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And OP is a noobie GC, so Larry used a simple way to explain the basic premise of protection in a way that would make sense to her.
 
jumper said:
And OP is a noobie GC, so Larry used a simple way to explain the basic premise of protection in a way that would make sense to her.
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But technically that is not the intent of an OCPD or the code. This has been brought up many times on DIY forums and licensed electricians have shot it down.

As is the wires on most heaters themselves are rated #12 buried in insulation, yet code requires #10.

Worse come to worse even a 50amp breaker would clear a fault as motor rules and grounding tables allow for much smaller conductors than table 310.15 B 16
 
jumper said:
The intent here is to answer the OP in a way that will not bewilder the crap out of her.:)

Wanna argue about that?:cool:
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I know I am splitting hairs- but I just think that future readers would get confused the other way around.

Technically code requires (like 422.11 E)- but why that is can be debated.
 
mbrooke said:
I know I am splitting hairs- but I just think that future readers would get confused the other way around.

Technically code requires (like 422.11 E)- but why that is can be debated.
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Start a different thread. Debate it there.

The instructions say 30A and the math with code sections say 30A, that is all that she needs to know. She needs to change the breaker.
 
jumper said:
You do realize that I may own a code book and possibly know how to use it.

I know the codes for WHs......
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I have a code book as well. :thumbsup:


(E) Single Non–Motor-Operated Appliance. If the branch
circuit supplies a single non–motor-operated appliance,
the rating of overcurrent protection shall comply with
the following:

(1) Not exceed that marked on the appliance.

(2) Not exceed 20 amperes if the overcurrent protection rating
is not marked and the appliance is rated 13.3 amperes
or less; or

(3) Not exceed 150 percent of the appliance rated current if
the overcurrent protection rating is not marked and the
appliance is rated over 13.3 amperes. Where 150 percent
of the appliance rating does not correspond to a
standard overcurrent device ampere rating, the next
higher standard rating shall be permitted.
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4500 watts = 18.75amps or 12.8 ohms

12.8 ohms at 208 volts is 3380 watts or 16.25amps

16.25 x 125%= 20.3125

next size up, 25 amps

150% of 16.25= 24.375


One could argue there is no listing at 208 volts, however some heater do have a 208 volt listing.


Yes I doubt the inspector would care or catch it, most do not and 30 is common at that voltage and wattage, but technically the code would require 25amps if followed to the letter.
 
Lets all be nice. IMO the electrician who wired the house ran out of #10 romex and pulled 8 to the hot water heater. When house was trimmed, electrician doing the panel saw a #8 and put on a 40A breaker.
 
kh1965 said:
Lets all be nice. IMO the electrician who wired the house ran out of #10 romex and pulled 8 to the hot water heater. When house was trimmed, electrician doing the panel saw a #8 and put on a 40A breaker.
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Possible, but OP never said size/type of old water heater. It may have needed a 40A circuit.

No additional info to go by.
 
mbrooke said:
LarryFine said:
The 40a breaker will continue to protect the circuit wiring, but the 30a breaker is needed to protect the water heater's internal wiring.
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I politely challenge this. To my knowledge there is nothing in any standard that requires and external OCPD to protect internal appliance wiring.
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Would you agree or disagree that the 30a breaker would do so better than the 40a breaker would?
 
steve66 said:
Maybe not for residential, but for commercial units, it is common to specify an option for simultaneous heating of both elements, and the manufacturers will provide it that way. It does give a faster recovery time for places like commercial kitchens.

9000 watts is also somewhat common.
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If it's spec'ed that way and it comes shipped that way that's one thing. Unauthroized field modification is another issue IMHO.
 
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